1. Field of the Invention
The present invention relates to a lead frame and an integrated circuit package having a structure with pins of very large number obtained by jointing the above lead frame to a semiconductor chip.
2. Description of the Related Art
FIG. 1 is a cross-sectional view showing a semiconductor device, i.e., an integrated circuit package in which a semiconductor chip can be connected to a circuit board or the like through an organic substrate having a projecting electrode formed of a solder ball or the like.
In FIG. 1, an organic multilayer circuit board a having about two to six layers formed of an organic material is mounted on its surface with a semiconductor tip b. An electrode of the semiconductor tip b and a wiring film c formed on a surface of the organic multilayer circuit board a are connected to each other by wire bonding employing metal wires d or the like.
A solder ball e is provided on a rear surface of the organic multilayer circuit board a and serve as a projecting electrode electrically connected through a through hole i to the wiring film c on the surface of the organic multilayer circuit board a. The solder ball e is faced to the outside through an opening of a solder resist film f. The semiconductor chip b together with the metal wire d are sealed by a sealing resin g.
An integrated circuit package j is formed such that the solder balls e formed on the rear surface of the organic multilayer circuit board a are connected to a circuit board h. Being provided with a large number of solder balls e arranged in a grid fashion, the organic multilayer circuit board a is often called a ball grid array (BGA). The integrated circuit package j employing the organic multilayer circuit board a is called a BGA package.
The BGA package j employs the wire bonding to connect the electrode of the semiconductor chip b with the wiring films c of the organic multilayer circuit board a. Therefore, this arrangement limits reduction of a pitch between electrode pads of the semiconductor chip b and inevitably enhances enlargement of the size of the semiconductor chip b.
The solder balls e in the BGA package j are provided physically. Therefore, when being set to predetermined positions, the solder balls e tend to be displaced, and there is a limit in arrangement of the solder balls e at a finer pitch. Since a large number of solder balls e are arranged in a grid fashion and the BGA package j is formed in a solid fashion by using the organic multilayer circuit board a, costs required for manufacturing the BGA package j is inevitably increased.
When the BGA package j is mounted on the circuit board h, the organic multilayer circuit board a sometimes becomes warped, which leads to the problem of the mounting.
The BGA package j cannot sufficiently radiate generated heat as a package having a large number pins, which prevents a high speed operation of the semiconductor device.
Since the solder balls e are formed in one layer, they cannot have both of satisfactory low-temperature bonding and satisfactory bonding strength.